Packaged peroxide formulation

ABSTRACT

A packaged peroxide formulation comprising a container and a liquid peroxide formulation, wherein said container has a volume of at least 50 litres and a vent area/volume ratio of at least 20·10 −3  m 2 /m 3 , said liquid peroxide formulation satisfies the classification tests for organic peroxide type F, has a conductivity of at least 100 pS/m, is not an emulsion or suspension, and comprises (i) at least 33 wt % of an organic peroxide selected from the group consisting of diacyl peroxides, peroxyesters, peroxydicarbonates, peroxyketals, and monoperoxycarbonates, and (ii) optionally a phlegmatiser, the packaged peroxide formulation has a vent area that is at least equal to the minimum total vent area as determined by the 10 litre venting test.

The invention relates to a packaged peroxide formulation that can behandled, produced, and shipped in a safe manner and which is suitablefor use in polymerisation and polymer modification processes.

Organic peroxides are liable to exothermic decomposition. They candecompose above a certain critical temperature to produce gas and heat.The heat produced promotes further decomposition. The storage andtransportation of these compounds is particularly troublesome in thatthe build-up of decomposition gases in the transportation or storagecontainer may cause violent, hazardous explosions, bursting thecontainer holding the peroxide. In recognition of this problem,international safety laws and standards regulate the transportation andstorage of these compounds.

The larger the container, the lower its surface-to-volume ratio, and themore difficult the transmittal of heat to the surroundings in case ofthermal decomposition. Hence, storage and transport of peroxides becomesmore hazardous when the container volume increases.

In order to improve transportation and storage safety, organic peroxidesare generally stored and transported in containers containing theperoxide diluted with one or more liquids, e.g. in the form of asuspension, emulsion, or solution. Aqueous peroxide emulsions orsuspensions are generally considered safe formulations, because theperoxide is dispersed in the water phase, which is well suited for theremoval of the heat of decomposing peroxide molecules, e.g. byconvection and/or evaporation.

The present invention relates to liquid peroxide formulations that arenot emulsions or suspensions. These formulations may consist of 100%pure liquid peroxide, but preferably contain a solvent that eitherdissolves the peroxide (in case of a solid peroxide) or dilutes theperoxide to form a homogeneous liquid (in case of a liquid peroxide).The solvent is also known as phlegmatiser. Classical phlegmatisingagents are hydrocarbons and esters, such as phthalates.

The larger the container, the more diluted a peroxide formulationgenerally needs to be. For instance, t-butyl peroxy-2-ethylhexanoate(Trigonox® 21) is presently transported in 30-litre containers in aconcentration up to 100 wt %. However, safety considerations havelimited the peroxide concentration in larger tanks to 30 wt % of theperoxide.

The presence of phlegmatiser has several disadvantages. For instance,when the peroxide formulation is used in a polymerisation reaction, thephlegmatiser may end up in the resin that is produced. This is evidentlyundesired. Further, from an economical viewpoint, it is undesired totransport and store large volumes which contain only a relatively smallamount of the actual reagent.

It is therefore an object of the present invention to provide safetransportation and storage of organic peroxides—without being suspendedor emulsified—in large containers (a volume of more than 50 litres) in ahigher concentration (i.e. at least 33 wt %), thereby decreasing thephlegmatiser content.

This object is achieved by the packaged peroxide formulation accordingto the present invention, which comprises a container and a liquidperoxide formulation, wherein

-   -   said container has a volume of at least 50 litres and a vent        area/volume ratio of at least 20·10⁻³ m²/m³,    -   said liquid peroxide formulation satisfies the classification        tests for organic peroxide type F, has a conductivity of at        least 100 pS/m, is not an emulsion or suspension, and        comprises (i) at least 33 wt % of an organic peroxide selected        from the group consisting of diacyl peroxides, peroxyesters,        peroxydicarbonates, peroxyketals, and monoperoxycarbonates,        and (ii) optionally a phlegmatiser, and    -   the packaged peroxide formulation has a vent area that is at        least equal to the minimum total vent area as determined by the        10 litre venting test.

The container in which the peroxide formulation is packaged has a volumeof at least 50 litres, preferably at least 200 litres, more preferablyat least 800 litres, and most preferably at least about 1,000 litres.The container volume preferably is not more than 20,000 litres, morepreferably not more than 10,000 litres.

The container must have an opening to quickly release the wholecontainer content in case a certain maximum pressure is exceeded, sothat an explosion can be avoided. The required size of this opening (thevent area) depends on, e.g., the volume of the container, the materialof which the container is made, and the type and concentration of theperoxide that is present in the container. The required minimum ventarea for a specific packaged formulation can be determined by the 10litre venting test as described in Amendment 1 to the 4^(th) revisededition of the Manual of Test and Criteria—ST/SG/AC.10/32/Add.2 (23 Feb.2005), Appendix 5—of the United Nations Recommendations on the Transportof Dangerous Goods.

The vent area/volume ratio of the container must be at least 20·10⁻³m²/m³, preferably at least 50·10⁻³ m²/m³, more preferably at least80·10⁻³ m²/m3, and most preferably at least about 100·10⁻³ m²/m³. Forpractical reasons, the vent area/volume ratio preferably is not higherthan 250·10⁻³ m²/m³, more preferably not higher than 125·10⁻³ m²/m³.

The packaged peroxide formulation according to the present invention ispreferably stored and transported at temperatures above −20° C.,preferably above −10° C., more preferably above 0° C. The preferredmaximum storage and transportation temperature is generally about 50° C.

A further advantage of the packaged peroxide formulation according tothe present invention is that ice formation—resulting from the smallamount of water that is generally present in peroxideformulations—during storage and transportation at temperatures below 0°C. is reduced. Ice formation may result in blocked and/or frozen valves,which may hamper the container unloading process.

The liquid peroxide formulation must satisfy the classification testsfor “organic peroxide Type F”, of the Manual of Tests and Criteria(4^(th) revised edition), Part II, Division 5.2 of United NationsRecommendations on the Transport of Dangerous Goods, resulting in aclassification UN 3109 and/or UN 3119. These tests are known to everyperson skilled in the art of organic peroxide chemistry.

The organic peroxide concentration in the liquid peroxide formulation isat least 33 wt %, preferably at least 35 wt %, more preferably at least40 wt %, and most preferably at least 45 wt %. The organic peroxideconcentration preferably is 90 wt % or less, more preferably 80 wt % orless, even more preferably 70 wt % or less, and most preferably 60 wt %or less. All weight percentages are based on the total weight of theperoxide formulation.

If the organic peroxide concentration is less than 100 wt %, the liquidperoxide formulation also contains a phlegmatiser.

The conductivity of the liquid peroxide formulation is at least 100pS/m, preferably at least 500 pS/m, more preferably at least 1,000 pS/m,more preferably still at least 2,000 pS/m, even more preferably at least4,000 pS/m. The conductivity can range up to 100,000 pS/m, if sodesired.

This conductivity is measured according to British Standard 5958, part1:1991 (Appendix A, chapter A.2.3; available from the British StandardsInstitution), using a voltage of 5 V.

The organic peroxide used in the present invention is selected fromdiacyl peroxides, peroxyesters, (cycli) perketals, peroxydicarbonates,and monoperoxycarbonates. Hence, the organic peroxide comprises one ormore peroxyester groups (of the formula —C(O)OO—), peroxy(di)carbonategroups (of the formula —OC(O)OO—), perketal groups (of the formula—O—C_(n)—OO—), or diacyl peroxide groups (of the formula —C(O)OOC(O)—).Also mixed peroxides (containing any two different peroxygen-bearingmoieties in one molecule) and mixtures of two or more of these peroxidescan be used. It is noted that if the organic peroxides are not liquid atroom temperature, they may be soluble in the phlegmatiser or mixture ofphlegmatisers. Although the peroxides can be oligomeric or polymeric innature, it is preferred that they are of the conventional typecomprising one, two or three peroxygen bonds in the molecule. Morepreferred are (di)peroxyesters and diacyl peroxides. Most preferred are(di)peroxyesters.

Examples of (di)peroxyesters are1,1,4,4-tetramethylbutyl-1,4-di(peroxy-2-methyl propa noate),tert-butylperoxy neodecanoate, tert-amylperoxy neodecanoate,1,1,3,3-tetramethyl butyl-1-peroxy neodecanoate, 1,1-dimethyl-3-hydroxybutyl-1-peroxy neodecanoate, tert-butylperoxy pivalate, tert-amylperoxypivalate, 1,1,3,3-tetramethyl butyl-1-peroxy pivalate,1,1-dimethyl-3-hydroxy butyl-1-peroxy pivalate, tert-butylperoxy 2-ethylhexanoate, tert-amyl peroxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutyl-1-peroxy 2-ethylhexanoate, 1,1-dimethyl-3-hydroxy butyl-1-peroxy2-ethyl hexanoate, tert-butylperoxy benzoate, tert-amylperoxy benzoate,1,1,3,3-tetramethyl butyl-1-peroxy benzoate, 1,1-dimethyl-3-hydroxybutyl-1-peroxy benzoate, tert-butylperoxy 3,3,5-trimethylhexanoate,tert-amylperoxy 3,3,5-trimethylhexanoate, 1,1,3,3-tetramethylbutyl-1-peroxy 3,3,5-trimethylhexanoate, 1,1-dimethyl-3-hydroxybutyl-1-peroxy 3,3,5-trimethylhexanoate, tert-butylperoxy isobutyrate,tert-amylperoxy isobutyrate, 1,1,3,3-tetramethyl butyl-1-peroxyisobutyrate, and 1,1-dimethyl-3-hydroxy butyl-1-peroxy iso butyrate.

Examples of diacyl peroxides are bis(3,3,5-trimethylhexanoyl) peroxide,dilauroyl peroxide and didecanoyl peroxide.

Examples of peroxydicarbonates are [di(4-tert-butylcyclohexyl)peroxy-dicarbonate, di(2-ethylhexyl) peroxydicarbonate, dibenzoylperoxide, dicetyl peroxydicarbonate, and dimyristyl peroxydicarbonate.

Examples of monoperoxycarbonates are tert-butylperoxy 2-ethylhexylcarbonate, tert-amylperoxy 2-ethylhexyl carbonate, and tert-butylperoxyisopropyl carbonate.

Examples of (cyclic) peroxyketales are 1,1-di(tert-butylperoxy)cyclohexane,1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane,2,2-di(4,4-di(tert-butylperoxy)cyclohexyl)propane, and3,6,9,-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane.

Suitable phlegmatisers include paraffinic and white oils, n-paraffins,iso-paraffins, aromatic hydrocarbons, and oxygenated hydrocarbons, suchas ethers, epoxides, and esters. More specific examples are toluene,xylene, (diesel) fuel, phthalates, adipates, epoxidised soybean oil,n-octane, n-decane, isododecane, and ethylbenzene.

Preferably, the packaged peroxide formulation is essentially free ofchlorinated species, since such species may lead to corrosion problemsor interfere with the polymerisation process in which the formulationsare used as a source of free radicals. Further, the packaged peroxideformulation does not require the use of an antistatic—such as an(in)organic acid or a salt thereof—for reaching the desiredconductivity. It is therefore desired that the packaged peroxideformulation does not contain an antistatic. Most preferably, theformulation consists of—meaning: contains nothing more than—organicperoxide and phlegmatiser.

The invention further relates to a method for producing a polymer bymeans of a radical polymerisation process using organic peroxide as asource of free radicals, which method involves transporting the packagedperoxide formulation according to the invention to a polymerisation unitand introducing the peroxide formulation into the polymerisationprocess. Examples of such polymerisation processes are processes to makepolyvinyl chloride, copolymers of vinyl chloride, poly(meth)acrylate(co)polymers, etc. Preferably, the process is a styrene suspension(co)polymerisation process or a high-pressure ethylene(co)polymerisation process. Comonomers that may be used in the(co)polymerisation process of ethylene are of the conventional type andinclude alkenes, such as propene, (cyclo)hexene and (cyclo)octene, andvinyl acetate. Comonomers that may be used in the (co)polymerisationprocess of styrene are of the conventional type and include divinylbenzene. The amount of organic peroxide used in these conventional(co)polymerisation processes will vary, depending on the polymerisationtemperature, the capacity for removing the heat of polymerisation, thekind(s) of monomer(s) used, and the applied pressure. Usually, from0.001-25 wt % of organic peroxide, based on the total weight of themonomers, is employed. Preferably, from 0.001-15 wt % of peroxide isemployed.

The invention also relates to a process for modifying a (co)polymer—suchas in cross-linking, grafting, and controlled degradation processes,e.g. the formation of polypropylene with another molecular weight and/ormolecular weight distribution—by transporting the packaged peroxideformulation according to the invention to a polymer modification unitand introducing the peroxide formulation into the process.

EXAMPLES Example 1

Stainless steel Intermediate Bulk Containers (IBCs) with a volume of1.25 m³ and a vent area/volume ratio of 100·10⁻³ m²/m³ were filled withthe liquid formulations listed below. These formulations containperoxide—either t-butyl peroxy-2-ethylhexanoate (Trigonox ® 21, ex AkzoNobel) or t-butyl peroxypivalate (Trigonox® 25, ex Akzo Nobel)—indifferent concentrations in isododecane. The conductivity of thedifferent formulations was measured according to British Standard 5958,part 1:1991 (Appendix A, chapter A.2.3; available from the BritishStandards Institution), using a voltage of 5 V.

Conductivity (pS/m) Peroxide concentration (wt %) Trigonox ® 21Trigonox ® 25 15 51.6 66.0 30 1.65 × 10³ 2.58 × 10³ 40 4.71 × 10⁴ 1.90 ×10⁴ 50 2.75 × 10⁵ 9.17 × 10⁴ 75 9.17 × 10⁵

Example 2

In order to evaluate their safety in transportation and storage, the 40wt % Trigonox® 25 and the 50 wt % Trigonox® 21 formulations of Example 1were tested using the 10 litre venting test according to the 4^(th)revised edition of the Recommendations on the Transport of DangerousGoods, Manual of Test and Criteria, ST/SG/AC.10/32/Add.2 (23 Feb. 2005),Appendix 5, using a vent area/volume ratio of 100·10⁻³ m²/m³ and heatingrates of 0.8 K/min and 0.7 K/min, respectively. The Trigonox® 25formulation resulted in a maximum recorded pressure of 4.5 barg; theTrigonox® 21 formulation resulted in a maximum recorded pressure of 0barg.

Since a stainless steel IBC can stand pressures up to 10 barg, theseformulations satisfy the 10 litre venting test, i.e. the vent area is atleast equal to the minimum total vent area.

Further, the classification tests for “organic peroxide Type F” wereperformed on these formulations, resulting in a classification of UN3109 and UN 3119.

Example 3

Computer model calculations (using ISPRA Relief) were performed todetermine the vent area/volume ratio that is required to stand the 10litre venting test for a stainless steal IBC containing the 40 wt %Trigonox® 25 formulation of Example 1.

A heating rate of 1.0 K/min was used in these calculations. The resultsare indicated in the Table below.

Vent area/volume ratio (m²/m³) Maximum recorded pressure (barg)  100 ·10⁻³ 0.1 77.0 · 10⁻³ 0.1 57.0 · 10⁻³ 0.1 39.3 · 10⁻³ 17 25.1 · 10⁻³ 5914.0 · 10⁻³ 95

Since a stainless steal IBC can stand a pressure of 10 barg, it followsthat a stainless steal IBC containing a 40 wt % Trigonox® 25 inisododecane formulation should have a vent area/volume ratio higher than39.3 m²/m³.

1. A packaged peroxide formulation comprising a container and a liquidperoxide formulation, wherein said container has a volume of at least 50litres and a vent area/volume ratio of at least 20·10⁻³ m²/m³, saidliquid peroxide formulation satisfies the classification tests fororganic peroxide type F, has a conductivity of at least 100 pS/m, is notan emulsion or suspension, and comprises at least 33 wt % of an organicperoxide selected from the group consisting of diacyl peroxides,peroxyesters, peroxydicarbonates, peroxyketals, andmonoperoxycarbonates, and the packaged peroxide formulation has a ventarea that is at least equal to the minimum total vent area as determinedby the 10 litre venting test.
 2. Packaged peroxide formulation accordingto claim 1 wherein the container has a volume in the range 200-10,000litres.
 3. Packaged peroxide formulation according to claim 1 whereinthe vent area/volume ratio of the container is at least 50·10⁻³ m²/m³.4. Packaged peroxide formulation according to claim 3 wherein the ventarea/volume ratio is at least 100·10⁻³ m²/m³.
 5. Packaged peroxideformulation according to claim 1 wherein the organic peroxide is aperoxyester or a diacyl peroxide.
 6. Packaged peroxide formulationaccording to claim 5 wherein the organic peroxide is a peroxyester. 7.Packaged peroxide formulation according to claim 3 wherein thephlegmatiser is selected from the group consisting of paraffinic andwhite oils, n-paraffins, iso-paraffins, aromatic hydrocarbons, ethers,epoxides, and esters.
 8. Packaged peroxide formulation according toclaim 1 wherein the conductivity of the liquid peroxide formulation isat least 1,000 pS/m.
 9. Packaged peroxide formulation according to claim8 wherein the conductivity of the liquid peroxide formulation is atleast 10,000 pS/m.
 10. Packaged peroxide formulation according claim 1wherein the organic peroxide concentration in the liquid peroxideformulation is in the range of 35-90 wt %.
 11. A method to produce apolymer by means of a radical polymerisation process using organicperoxide as a source of free radicals, the method comprisingtransporting a packaged peroxide formulation according to claim 1 to apolymerisation unit and introducing the liquid peroxide formulation intothe polymerisation process.
 12. A method to modify a (co)polymercomprising transporting a packaged peroxide formulation according toclaim 1 to a polymer modification unit and introducing the liquidperoxide formulation into the process.
 13. Packaged peroxide formulationaccording to claim 1 wherein the liquid peroxide formulation furthercomprises a phlegmatiser.
 14. Packaged peroxide formulation according to2 wherein the vent area/volume ratio of the container is at least50·10⁻³ m²/m³.
 15. Packaged peroxide formulation according to 13 whereinthe vent area/volume ratio of the container is at least 50·10⁻³ m²/m³.16. Packaged peroxide formulation according to claim 2 wherein theorganic peroxide is a peroxyester or a diacyl peroxide.
 17. Packagedperoxide formulation according to claim 13 wherein the organic peroxideis a peroxyester or a diacyl peroxide.
 18. Packaged peroxide formulationaccording to claim 5 wherein the conductivity of the liquid peroxideformulation is at least 1,000 pS/m.
 19. Packaged peroxide formulationaccording to claim 13 wherein the conductivity of the liquid peroxideformulation is at least 1,000 pS/m.
 20. Packaged peroxide formulationaccording to claim 8 wherein the organic peroxide concentration in theliquid peroxide formulation is in the range of 35-90 wt %.